In fuel injection systems of the port injection or throttle body type, fuel is supplied under pressure to electronically control fuel injectors which open and close to supply the fuel under pressure to the cylinders of the engine. It is common to provide a fuel pressure regulator downstream of the inlet to the fuel rail which functions upon application of fuel to cause a diaphragm assembly to move away form a valve seat to control the fuel flow from a fuel pump supply through the inlet and through the outlet of the regulator and to the tank. Pressure is maintained at the desired pressure differential between the pump and the outlet of the regulator. The fuel pump displaces a fixed flow rate so the amount of fuel returned to the tank varies with engine speed, the largest return rate occurring at idle. When the fuel pump is stopped the regulator starts to close then acts as a shut off valve to maintain pressure on the system. Fuel pressure regulators which can be used are such as shown in U.S. Pat. Nos. 3,511,270, 4,237,924 and 4,627,463.
It has been found that in such systems, when the engine is shut off, the system pressure may cause leakage pass the injector nozzles so that when the engine is restarted there may exist a long crank condition, a no start condition, a back fire condition and/or a high fuel emission condition. In addition there may be fuel noise when the engine is running due to the pressures know "hammer".
Among the objects of the present invention are to provide a fuel system which overcomes these problems.
In accordance with the invention, the fuel supply system for internal combustion engines wherein fuel is supplied to a fuel rail and, in turn, to fuel injectors which are electronically controlled to provide fuel to the cylinders of the engine including a fuel pressure regulator for controlling the pressure of fuel support to the fuel rail. A fuel bypass and damper device is provided upstream of the fuel pressure regulator and is operable to reduce the pressure of fluid in the fuel rail when the engine is shut off to provide a lower pressure in the fuel rail and fuel injector nozzles and bypass any excess fuel. The device further functions to dampen the noise when the engine is running. Such as system overcomes the problems of leakage of the injectors due to the high pressure retained in the system which in turn may produce long crank conditions, no start conditions, back fire conditions or high fuel emission conditions as well as engine noises.